text: An interesting application for using glow discharge was described in a 2002 scientific paper by Ryes, Ghanem et al.
  According to a Nature news article describing the work, researchers at Imperial College London demonstrated how they built a mini-map that glows along the shortest route between two points.  The Nature news article describes the system as follows:
  :To make the one-inch London chip, the team etched a plan of the city centre on a glass slide. Fitting a flat lid over the top turned the streets into hollow, connected tubes. They filled these with helium gas, and inserted electrodes at key tourist hubs. When a voltage is applied between two points, electricity naturally runs through the streets along the shortest route from A to B - and the gas glows like a tiny neon strip light.
  The approach itself provides a novel visible analog computing approach for solving a wide class of maze searching problems based on the properties of lighting up of a glow discharge in a microfluidic chip.